1823. Jon Bee, Dict. of the Turf, etc. They were invariably thieves and gamblers who used flash formerly; but other kinds of persons, now-a-day, who may be rippishly inclined, adopt similar terms and phrases, to evince their uppishness in the affairs of life. These gentlemen also consider all terms of art and of science as flash; ... of course, those words and sayings which are appropriate to the turf, the ring, and field sports, are equally considered as flash by them, and the word has been applied (too generally we allow), to all this species of quid pro quo lingo. 3. (old).—See quot. and cf., with a Shaksperian gloss of flash = a burst of wit or merriment. 1748. T. Dyche, Dict. (5th ed.), flash (s.), also a boast, brag, or great pretence made by a spendthrift, quack, or pretender to more art or knowledge than he really has. 4. (old).—A showy swindler. (e.g., the Sir Petronel Flash of quot.); a blustering vulgarian. 1605. Marston, Jonson, and Chapman, Eastward Hoe! iv. 1. ‘Sir Petronel Flash, I am sorry to see such flashes come from a gentleman of your quality.’ 1632. Shirley, Love in a Maze, i., 2. The town is full of these vainglorious flashes. 5. (old).—A peruke or perriwig. 1690. B. E., New Dict. of the Canting Crew, s.v. 1785. Grose, Dict. of the Vulgar Tongue. Rum flash, a fine long wig. Queer flash, a miserable weather-beaten caxon. 6. (common).—A portion; a drink; or go (q.v.). Cf., Flash of Lightning, sense 1. Adj. (common).—1. Relating to thieves, their habits, customs, devices, lingo, etc. 1782. Geo. Parker, Humorous Sketches, p. 34. No more like a kiddy he’ll roll the flash song. 1830. Lytton, Paul Clifford, ‘Long Ned’s Song.’ And rarely have the gentry flash, In sprucer clothes been seen. 1837. Dickens, Oliver Twist, ch. viii. I suppose you don’t know what a beak is, my flash com-pan-i-on. 1857. Snowden, Mag. Assistant, 3rd ed., p. 448. I have seen Cheeks (a flash name for an accomplice). 1863. C. Reade, Hard Cash, II., 244. He used some flash words, and they were shown into a public room. 1864. Cornhill Magazine, ii., 336. In the following verse, taken from a pet flash song, you have a comic specimen of this sort of guilty chivalry. 2. (thieves’).—Knowing; expert; showy. Cf., down, fly, wide-awake, etc. Hence (popularly), by a simple transition, vulgarly counterfeit, showily shoddy: possibly the best understood meanings of the word in latter-day English. To put one flash to anything = to put him on his guard; to inform. 1819. Moore, Tom Crib’s Memorial, p. 19. Another philosopher, Seneca, has shown himself equally flash on the subject. 1835. Dickens, Sketches by Boz, p. 17. Laying aside the knowing look, and flash air, with which he had repeated the previous anecdote.